[PATCH] drm/i915: Avoid rcu_barrier() from reclaim paths (shrinker)
Chris Wilson
chris at chris-wilson.co.uk
Tue Mar 14 10:55:11 UTC 2017
The rcu_barrier() takes the cpu_hotplug mutex which itself is not
reclaim-safe, and so rcu_barrier() is illegal from inside the shrinker.
[ 2566.458979] ======================================================
[ 2566.459054] [ INFO: possible circular locking dependency detected ]
[ 2566.459127] 4.11.0-rc1+ #26 Not tainted
[ 2566.459194] -------------------------------------------------------
[ 2566.459266] gem_streaming_w/759 is trying to acquire lock:
[ 2566.459334] (&obj->mm.lock){+.+.+.}, at: [<ffffffffa034bc80>] i915_gem_object_pin_pages+0x0/0xc0 [i915]
[ 2566.459605]
[ 2566.459605] but task is already holding lock:
[ 2566.459699] (&mm->mmap_sem){++++++}, at: [<ffffffff8106fd11>] __do_page_fault+0x121/0x500
[ 2566.459814]
[ 2566.459814] which lock already depends on the new lock.
[ 2566.459814]
[ 2566.459934]
[ 2566.459934] the existing dependency chain (in reverse order) is:
[ 2566.460030]
[ 2566.460030] -> #1 (&mm->mmap_sem){++++++}:
[ 2566.460139] lock_acquire+0xfe/0x220
[ 2566.460214] down_read+0x4e/0x90
[ 2566.460444] i915_gem_userptr_get_pages+0x6e/0x340 [i915]
[ 2566.460669] ____i915_gem_object_get_pages+0x8b/0xd0 [i915]
[ 2566.460900] __i915_gem_object_get_pages+0x6a/0x80 [i915]
[ 2566.461132] __i915_vma_do_pin+0x7fa/0x930 [i915]
[ 2566.461352] eb_add_vma+0x67b/0x830 [i915]
[ 2566.461572] eb_lookup_vmas+0xafe/0x1010 [i915]
[ 2566.461792] i915_gem_do_execbuffer+0x715/0x2870 [i915]
[ 2566.462012] i915_gem_execbuffer2+0x106/0x2b0 [i915]
[ 2566.462152] drm_ioctl+0x36c/0x670 [drm]
[ 2566.462236] do_vfs_ioctl+0x12c/0xa60
[ 2566.462317] SyS_ioctl+0x41/0x70
[ 2566.462399] entry_SYSCALL_64_fastpath+0x1c/0xb1
[ 2566.462477]
[ 2566.462477] -> #0 (&obj->mm.lock){+.+.+.}:
[ 2566.462587] __lock_acquire+0x1602/0x1790
[ 2566.462661] lock_acquire+0xfe/0x220
[ 2566.462893] i915_gem_object_pin_pages+0x4c/0xc0 [i915]
[ 2566.463116] i915_gem_fault+0x2c2/0x8c0 [i915]
[ 2566.463197] __do_fault+0x42/0x130
[ 2566.463276] __handle_mm_fault+0x92c/0x1280
[ 2566.463356] handle_mm_fault+0x1e2/0x440
[ 2566.463443] __do_page_fault+0x1c4/0x500
[ 2566.463529] do_page_fault+0xc/0x10
[ 2566.463613] page_fault+0x1f/0x30
[ 2566.463693]
[ 2566.463693] other info that might help us debug this:
[ 2566.463693]
[ 2566.463820] Possible unsafe locking scenario:
[ 2566.463820]
[ 2566.463918] CPU0 CPU1
[ 2566.463988] ---- ----
[ 2566.464068] lock(&mm->mmap_sem);
[ 2566.464143] lock(&obj->mm.lock);
[ 2566.464226] lock(&mm->mmap_sem);
[ 2566.464304] lock(&obj->mm.lock);
[ 2566.464378]
[ 2566.464378] *** DEADLOCK ***
[ 2566.464378]
[ 2566.464504] 1 lock held by gem_streaming_w/759:
[ 2566.464576] #0: (&mm->mmap_sem){++++++}, at: [<ffffffff8106fd11>] __do_page_fault+0x121/0x500
[ 2566.464699]
[ 2566.464699] stack backtrace:
[ 2566.464801] CPU: 0 PID: 759 Comm: gem_streaming_w Not tainted 4.11.0-rc1+ #26
[ 2566.464881] Hardware name: GIGABYTE GB-BXBT-1900/MZBAYAB-00, BIOS F8 03/02/2016
[ 2566.464983] Call Trace:
[ 2566.465061] dump_stack+0x68/0x9f
[ 2566.465144] print_circular_bug+0x20b/0x260
[ 2566.465234] __lock_acquire+0x1602/0x1790
[ 2566.465323] ? debug_check_no_locks_freed+0x1a0/0x1a0
[ 2566.465564] ? i915_gem_object_wait+0x238/0x650 [i915]
[ 2566.465657] ? debug_lockdep_rcu_enabled.part.4+0x1a/0x30
[ 2566.465749] lock_acquire+0xfe/0x220
[ 2566.465985] ? i915_sg_trim+0x1b0/0x1b0 [i915]
[ 2566.466223] i915_gem_object_pin_pages+0x4c/0xc0 [i915]
[ 2566.466461] ? i915_sg_trim+0x1b0/0x1b0 [i915]
[ 2566.466699] i915_gem_fault+0x2c2/0x8c0 [i915]
[ 2566.466939] ? i915_gem_pwrite_ioctl+0xce0/0xce0 [i915]
[ 2566.467030] ? __lock_acquire+0x642/0x1790
[ 2566.467122] ? __lock_acquire+0x642/0x1790
[ 2566.467209] ? debug_lockdep_rcu_enabled+0x35/0x40
[ 2566.467299] ? get_unmapped_area+0x1b4/0x1d0
[ 2566.467387] __do_fault+0x42/0x130
[ 2566.467474] __handle_mm_fault+0x92c/0x1280
[ 2566.467564] ? __pmd_alloc+0x1e0/0x1e0
[ 2566.467651] ? vm_mmap_pgoff+0x160/0x190
[ 2566.467740] ? handle_mm_fault+0x111/0x440
[ 2566.467827] handle_mm_fault+0x1e2/0x440
[ 2566.467914] ? handle_mm_fault+0x5d/0x440
[ 2566.468002] __do_page_fault+0x1c4/0x500
[ 2566.468090] do_page_fault+0xc/0x10
[ 2566.468180] page_fault+0x1f/0x30
[ 2566.468263] RIP: 0033:0x557895ced32a
[ 2566.468337] RSP: 002b:00007fffd6dd8a10 EFLAGS: 00010202
[ 2566.468419] RAX: 00007f659a4db000 RBX: 0000000000000003 RCX: 00007f659ad032da
[ 2566.468501] RDX: 0000000000000000 RSI: 0000000000100000 RDI: 0000000000000000
[ 2566.468586] RBP: 0000000000000007 R08: 0000000000000003 R09: 0000000100000000
[ 2566.468667] R10: 0000000000000001 R11: 0000000000000246 R12: 0000557895ceda60
[ 2566.468749] R13: 0000000000000001 R14: 00007fffd6dd8ac0 R15: 00007f659a4db000
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
---
drivers/gpu/drm/i915/i915_gem_shrinker.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c b/drivers/gpu/drm/i915/i915_gem_shrinker.c
index 006a8b908f77..4fda4d70d0f9 100644
--- a/drivers/gpu/drm/i915/i915_gem_shrinker.c
+++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c
@@ -266,7 +266,7 @@ unsigned long i915_gem_shrink_all(struct drm_i915_private *dev_priv)
I915_SHRINK_ACTIVE);
intel_runtime_pm_put(dev_priv);
- rcu_barrier(); /* wait until our RCU delayed slab frees are completed */
+ synchronize_rcu(); /* wait for our RCU delayed slab frees */
return freed;
}
--
2.11.0
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